1. Field of Invention
The present invention relates to an oil pump system of a hybrid vehicle and a method for controlling the same, and more particularly, to an oil pump system of a hybrid vehicle, which is provided to supply a hydraulic pressure to an automatic transmission using only an electric oil pump, and a method for controlling the same.
2. Description of Related Art
In general, an automatic transmission is connected to an oil pump system for supplying an operating hydraulic pressure to the automatic transmission. The oil pump system includes one or more oil pumps.
Conventionally, an oil pump system which supplies an operating hydraulic pressure to an automatic transmission using a mechanical oil pump and an electric oil pump together has been mainly used. In particular, hybrid vehicles have mainly employed a control method of an oil pump system, which divides a running state of a vehicle into a stoppage section, a low-speed section, and a high-speed section, and selectively operates a mechanical oil pump and an electric oil pump. According to the control method of the oil pump system, only the electric oil pump may be operated during the stoppage section, the mechanical oil pump and the electric oil pump may be simultaneously operated during the low-velocity section, and only the mechanical oil pump may be operated during the high-velocity section.
However, when two or more oil pumps such as the mechanical oil pump and the electric oil pump are used, the production cost may excessively increase. Furthermore, the mechanical oil pump operated by driving torque of an engine may serve as a factor having a bad influence on the fuel efficiency of the vehicle. When one of the mechanical oil pump and the electric oil pump is omitted, an operating hydraulic pressure may not be stably supplied to the automatic transmission. In particular, when only the electric oil pump is used, it is not easy to perform a control operation for dealing with a defect which may occur in supplying a hydraulic pressure to the automatic transmission, due to a trouble of a solenoid or the like. Furthermore, when a hydraulic pressure required for the electric oil pump is set to be fixed to an excessively high hydraulic pressure at the time at which a hydraulic pressure supply defect occurs, power may be wasted to drive the electric oil pump, and parts may be damaged by over-current.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.